Stadimeter



T. o. BRANDON STADIMETER Filed Oct. 30, 1943 July -1 6; 1946.

W. 2 O 2 a .m mm NM wBMuTa m. T o T m O my Y B 3 a m w x 8 E m m Patented July 16, 1946 UNITED STATES PATENT OFFICE 1 Claim.

My invention relates to optical devices for measuring distances, and in particular to such devices classified as stadimeters.

One of the most useful devices aboard ship is the stadimeter, by which means the distance of an object is quickly indicated if a dimension such as its height is known, or by which its dimension is indicated if its distance is known.

It is a primary object of my invention to provide a stadimeter of simplified and more sturdy construction and in which the manufacturing and maintenance costs are materially reduced.

It is another main object of my invention to provide a stadimeter wherein the device which carries the distance indicating drum is carried by a support pivotally attached to the main frame, and bears resiliently against the index bar which is also pivotally attached to the main frame and carries the index mirror.

These, and other objects will become apparent as the description progresses, and from the draw.- ing, wherein:

Fig. 1 is a side elevational View of the stadimeter;

Fig. 2 is a bottom view of the device; and

Fig. 3 is a sectional view along the line 3-3 of Fig. 1 looking in the direction of the arrows.

As shown in the drawing a three-sided main frame II] has two straight sides 29 and 2| meeting at an apex 25 opposite to its third side 22 which is a circular arc. Web members 23 extend between the sides of the main frame.

An arm 24 extend from the apex 25 of the frame to beyond the circular side 22, and is pivoted at one end in a bearing (not shown) at the apex 25, so that the arm swings about the center of the arc of the circular side 22. At the outer end of arm 24 is a lug I (Fig. 3) which may be either integral with arm 24 or fastened to it by means not shown. As shown in Fig. 3 the lug I5 has a downwardly extending flange which extends under the circular side 22 of the main frame It. A clamp screw 9 is threaded into this flange, and when tightened it clamps the arm 24 to the circular side 22 at any desired position along its arc.

Lug I5 also has a projection 26 shown in Figs. 1 and 3 which has a portion overlying the circular side 22. Projection 26 has a scratch line 2'! drawn radially to the center of the arc of side 22 to furnish an indicator to read the position of arm 24 along the side 22. The side 22 has graduations 28 inscribed on it as shown in Fig. 1, against which scratch line 21 is read.

Also forming a part of lug I5 is an upwardly amended April 30, 1928; 370 O. G. 757) extending boss 29 (Fig. 3) which is drilled and tapped to receive a drum screw IT. A drum I8 is fixed to the outer end of screw I1. The inner end of screw I 1 is conical but terminates in a ball portion 30 which is received and held by a spherical socket in asliding angled member l5. Member Hi has a fiat bottom portion which slides radially along arm 24 as screw I! is rotated by means of the drum I8. A helical scale 3| is inscribed on the periphery of the cylindrical surface of the drum I8 and is graduated in terms of distance. A pointer 32 is fixed to the boss 29 as shown in Fig. 1, and overlies the scale 3|. In conjunction with the scale 3| the pointer 32 indicates the lon itudinal and radial position of screw I! in terms of the distance of the object the stadimeter is sighted An index arm I4 has a circular curvature about the same center as the circular side 22, .but with a smaller radius as shown in Fig. 1. The index arm I4 is pivotally mounted at one end in a bearing (not shown) in a boss 33 on the frame I0 near the juncture of sides 2| and 22, and is raised above the plane of the frame II] to provide space for the arm 24.

Fixedly mounted on the arm 24 is a tube l9 enclosing a coil spring (not shown) and guiding a plunger 34 which telescopes into tube l9 and against the spring. Plunger 34 is thereby resiliently urged outwardly. The index arm [4 is thereby constantly and resiliently held against the angled slide member IS on the drum screw I'I. Thus when slide member It is moved inwardly or outwardly by rotation of the drum I8 and screw I1, the index arm I4 is rotated about its pivot in the boss 33. Since the tangent to index arm I4 will not always be normal to the drum screw ll, as it is when in the position shown in Fig. 1, the universal connection between the ball 30 and member It provides for proper alignment of member I6 with the index arm I4.

A horizon mirror I2 is fixed to. the frame II} on the side 20, and any common means (not shown) may be included to provide for adjustment of the mirror in its mounting. Only half of mirror I2 is silvered; as shown in Fig. 2 the portion above line 4-4 being clear or translucent glass, and the portion below line 4-4 being silvered on the side toward the eyepiece II. An index mirror I3 is similarly fixed t0 the index arm I4 at its pivoted end. Mirror I3 is silvered over its entire surface on the side facing mirror i2.

An extension 35 on the frame Iflprovides a mounting for a telescopic eyepiece II which is in alignment with mirror [2.

In operation, assuming that the dimension of an object, such as the height of a ship, is known, clamp screw 9 is loosened and the arm 24 is moved about its pivot until the scratch line 21 coincides with the graduation 28 on the arcuate side 22 that corresponds to the known dimension. Screw 9 is tightened. Then the instrument is held so that the ship is seen through the eyepiece H and the unsilvered portion of mirror l2. The drum I8 is then rotated until the image of the ships masthead, reflected from the mirror [3 and then from the silvered portion of mirror [2, coincides with the ships waterline as seen directly through the unsilvered portion of the mirror I2. If the length of the ship is known instead of its height, then the instrument will be held in the position shown in Fig. '2 and its distance found by setting arms 24 and l 4 in a-manner similar to that described above, and the bow and stern will be made to coincide in the clear and silvered portions of mirror I2.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

I claim:

In a stadimeter, a main frame having a circular arcuate side; a horizon mirror mounted in relatively fixed position on said frame; an eyepiece fixed to said frame in alignment with and spaced from said horizon mirror; a curved index arm mounted on said frame for pivotal movement about an axis adjacent one end of said arcuate side, said index arm being adjacent to said arcuate side and substantially concentric with said arcuate side when in operating position; an index mirror mounted on said index arm substantially at its pivotal mounting; a second arm mounted on said frame for pivotal movement about an axis coinciding with the center of said arcuate side, the other end of said arm slidably engaging said arcuate side; clamping means to fix said second arm against rotation; screw means mounted for radial movement on said second arm to rotate said index arm about its pivot; a slide member universally connected to said screw means and engaging the lower edge of said index arm; a spring-biased member onsaid second arm opposed to the slide member to urge the index arm resiliently against the slide member; and scale means to indicate the positions of said arms with respect to said frame, including graduations on said arcuate side, a graduated drum on the outer end of said screw means, and indicating means on said second arm.

THOMAS O. BRANDON. 

